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Chemistries of potable water differ considerably from place to place; important differences exist in the amounts of dissolved oxygen, hardness, as well as in a variety of other substances and gases dissolved in and carried by the water. Water may also include suspended material, such as clay particles, and bacteriological and biological contaminants. These impurities often adversely affect the many uses of water in society.
Dissolved gases, dissolved unwanted substances and suspended contaminants unfavorably affect the quality of drinking water. Hydrogen sulfide, sodium sulfite and ammonia, present in some regional drinking waters, even in minute amounts cause the water to have an unpleasant taste. Hardness, determined by the presence of calcium or magnesium carbonate or bicarbonate or combinations thereof, affects water's taste and appearance. Also, salts dissolved in water may tend to precipitate as a scum in hot beverages, such as coffee or tea. In addition, they affect the clarity of ice when such water is frozen. Further, dissolved gases, such as oxygen, are responsible for negative consequences relative to the appearance and taste of water, the taste of hot beverages, such as coffee, as well as the pellucidity of ice. These dissolved gases, substances and suspended contaminants thus constitute a continuing problem to those concerned with the taste and appearance of water, hot and cold beverages and ice.
Moreover, the problem is aggravated when the water is to be carbonated. The presence of dissolved gases, especially oxygen, and contaminants, particularly hardness, reduces water's capacity for carbonation. The result is that carbonated drinks are almost always less tasty because of reduced carbonation, and therefore less desirable to consumers.
Fountain beverage dispensers have been installed in bars, restaurants, drug stores and other locations on a worldwide basis which include apparatus for carbonating water received from a source of potable water, and mixing it with a flavored syrup to make a variety of soft drinks as well as alcoholic beverages. Although water may be treated at the point of use for removing or neutralizing contaminants in the local water supply, the various known and more frequently used modes of municipal water treatment seldom improve water sufficiently for optimum subsequent carbonation.
Also, it is not uncommon to provide an apparatus for softening water at the point of use. One method of softening water is to pass it through granular zeolite, which may be a natural occurring or artificially hydrated aluminum silicate, wherein the water softening action occurs due to the zeolite replacing calcium ions from the water with the zeolite's sodium ions. However, the addition of sodium to drinking water is deleterious for those with low-sodium dietary needs. Also, for the purposes of carbonation, sodium is considered undesirable as it, primarily from 20 ppm and up, destroys carbonation and thus should not be introduced into the water prior to carbonation.
Furthermore, dissolved gases, and other unwanted substances and suspended contaminants serve to impair the quality of water for other uses. For example, in the food packaging industry, water is often used as a medium in which to immerse the food to be packaged and preserved. The presence of gases, especially oxygen, many dissolved substances, as well as water's hardness, and suspended solids in the water medium have a pernicious effect on the preservation and taste of the packaged food. Also, the quality of water for domestic water heaters is an important concern in the industry; it is not unusual to place a water softener before a hot water heater to prevent calcification of the heat transfer surfaces in area of high water hardness. But this does little to remove dissolved gases that affect the efficiency of the heat transfer surfaces and the transfer of heat to and from the water. Additionally, the removal of oxygen and other contaminants from water added to boilers for "wet lay-up" has long been an industrial requirement.
There is therefore a need for a filter that can remove dissolved gases, other unwanted dissolved substances and suspended contaminants from common domestic water to improve its quality for a variety of purposes. The instant invention relates to a form of potassium aluminosilicate which has a chemical formula of particular types of zeolite and is produced in a manner similar to the production of certain types of zeolite. However, in its operable chemical and physical formulation, typical zeolite crystalline structures have not been detected by X-ray diffraction. Yet, because of its similarities to known zeolites both chemically and in the manufacture thereof, the instant invention is considered a zeolite.
In general, zeolites are molecular sieves that are unusually crystalline, hydrated aluminosilicates of monovalent or polyvalent bases which are able to adsorb and desorb water without changes to their crystal structure, and to adsorb elements and other compounds with the water removed. They are also capable of cation exchange.
Known zeolites are often formed by first a ripening or aging process for periods from several hours up to about nine days at ambient temperatures, that is, temperatures between 13.degree. C. and 38.degree. C. Following the ambient temperature or digestion step, the mixture is crystallized, which is accomplished generally at a temperature which may be the ambient temperature or one much higher. For example, crystallization may take place at temperatures from 20.degree. C. to as high as 125.degree. C. For commercial purposes, crystallization is usually effected at temperatures in the range of about 80.degree. C. to 125.degree. C. Not only is it more rapid, but also at lower temperatures the resulting crystals are often smaller in size than those formed at a higher temperature.
The chemical formula for a zeolite known as zeolite Y, expressed in terms of moles of oxides, may be written as: 0.9.+-.0.2 Na.sub.2 O:Al.sub.2 O.sub.3 :wSiO.sub.2 :xH.sub.2 O, wherein w is a value greater than about three up to about six, and x may be a value up to about nine. Such zeolite is disclosed along with a number of examples in U.S. Pat. No. 3,130,007, of D. Breck, which issued Apr. 21, 1964. Although, this zeolite Y is asserted to be a particularly effective adsorbent of oxygen, my attempts to use zeolite Y, as such, to achieve an effective removal of oxygen from water have been unsuccessful.